With VLSI designs entering multi-million gate count range, the yield of embedded memories is becoming a limiting factor for the overall yield for Integrated Circuit manufacturing. Memory built-in self-repair (BISR) techniques can help improve the yield of embedded memories. The memory BISR capability allows an IC device to continue to function despite the presence of defect(s) in its embedded memories. With memory BISR, faulty or defective memory blocks are identified and replaced with “redundant” memory block(s). These redundant memory blocks are pre-allocated memory blocks within a chip to be used for BISR purposes. By contrast, regular memory blocks are called “base” blocks.
Two methods for memory BISR have been proposed previously by Nicolaidis, et al. (2003). In the first method, as illustrated in FIG. 1, a memory block once identified as faulty is replaced by its closest fault-free block. This fault-free block, used for repair, can either be a base block or a redundant block. In another method, as illustrated in FIG. 2, a memory block identified as faulty can only be replaced by a designated redundant block. Both methods require using multiplexers (MUXes) to perform memory read/write operations for input data pins. The presence of the MUXes will slow down the operating speed of the memory.